1. Field of the Disclosed Subject Matter
The disclosed subject matter relates to catheters used in the delivery of a medical device, such as a self-expanding stent, for treating the luminal systems of a patient. Specifically, the disclosed subject matter relates to a delivery catheter having a retractable sheath moved by hydraulic chambers.
2. Description of the Related Art
A variety of systems using a retractable sheath are known for intraluminal delivery of a medical device, such as a stent or filter. However, there remains a need for continued improvement of such known delivery systems.
An example of such a delivery system is described in U.S. Pat. No. 6,425,898 to Wilson et al., which is incorporated by reference herein, wherein a delivery system is provided having an inner member with a stop attached to the inner member. During deployment, the stop prevents the stent from migrating proximally during retraction of the sheath for stent deployment.
Conventional self-expanding stent delivery systems generally comprise a handle portion and an elongated shaft, wherein the stent is disposed within a delivery portion at the distal end of the shaft. To deploy the stent, an outer sheath is provided which can be retracted relative to the stent to release the stent from its delivery configuration. The sheath in such systems generally spans the full length of the catheter resulting in an increased profile and stiffness over the entire length of the catheter. Further, because the sheath spans the full length of the catheter there is an increased risk of the sheath binding with other components of the catheter during passage through the tortuous luminal system of a patient, thus inhibiting the deployment of the stent.
Another issue with such delivery systems is that the sheath is generally pulled back in a 1-to-1 ratio with the user's input (force). Because the stent may embed in the outer sheath during storage and shipping, and due to larger static friction forces, a large amount of initial input is typically required to release the stent which may lead to incorrect placement. When initially releasing the stent, it may be desirable to slowly pull back the sheath for proper placement and then more readily retract the sheath to prevent inadvertent movement of the stent.
Further, the amount of force that is required to retract the sheath, particularly for stents of greater length as required for peripheral indications, can be substantial. Therefore there is a need for an improved delivery system for self-expanding stents having reduced force requirements for delivery of a medical device.
There thus remains a continued need for an efficient and economic system for delivering a medical device that is easy to use and provides accurate stent placement. The presently disclosed subject matter satisfies these and other needs.